1. Field of the Invention
The invention relates to a method and a system for cooling and washing biomass syngas.
2. Description of the Related Art
Like the coal gas production, the biomass gas production requires cooling and washing. Currently, the purification of the biomass syngas mainly adopts conventional method for cooling and washing the coal gas.
The cooling of the coal gas generally is conducted in the gasifier, out of the gasifier, or a combination thereof.
When water is used to cool the syngas in the gasifier, the gasifier has a complicate structure and a large size. Slag easily adheres to a wall surface of the gasifier, scale easily forms on the water side of the gasifier, and hidden dangers, like pipe explosion and perforation and water leakage, exist. When gas is used to cool the syngas in the gasifier, the gas consumption is large, the mixed gas increases by a large volume, so that dimensions of the subsequent devices correspondingly increase. In addition, the main process and the circulating coal gas process require large energy consumption.
When water is used to cool the syngas out of the gasifier, the temperature of the syngas is cooled to between 200 and 300° C., however, this method is only applicable to particular chemical syngas, thereby having large limitation.
When the high temperature syngas is cooled by using a radiation waste heat boiler, the waste heat boiler is required to have relatively large heating surface of the slag, and has to be equipped with a particular dust removal device, which increases the device investment.
Methods for removing dust from coal gas include: precipitation, filter, cyclone precipitation, electric precipitation, water washing, and dust removal by Venturi scrubber. Different dust removal methods vary in the effect of the dust removal and the resistance consumption.
Characteristics of different syngas produced from different raw materials and by different gasification processes are not all the same. However, targeted process method and system configuration should be adopted to ensure advanced purification target and economy target. Characterized in complicate system, long procedure, high energy consumption, low efficiency and stability, and being uneconomic, the conventional methods for coal gas purification must be optimized and developed when it is applied to treat the biomass syngas.